1. Field of the Invention
The present invention relates to a C-arm holding apparatus and an X-ray diagnostic apparatus and, more particularly, to a floor type C-arm holding apparatus which holds an X-ray generating unit and an X-ray detecting unit so as to make them face each other, and an X-ray diagnostic apparatus having the C-arm holding apparatus.
2. Description of the Related Art
Medical imaging diagnostic techniques using X-ray diagnostic apparatuses, MRI apparatuses, and X-ray CT apparatuses have rapidly advanced with improvements in computer technology, and have become indispensable to current medical practice.
Recently, X-ray diagnosis has advanced mainly in the field of circulatory organs with improvements in catheter techniques. An X-ray diagnostic apparatus for the diagnosis of circulatory organs generally comprises an X-ray generating unit, an X-ray detecting unit, a holding apparatus which holds the X-ray generating unit and the X-ray detecting unit, a table top, a signal processing unit, a display unit, and the like. The holding apparatus allows X-ray imaging at an optimal position or in an optimal direction by pivoting, rotating, or moving a C-arm or Ceiling-traveling C or Ceiling-mounted arm around a patient (to be referred to as a subject hereinafter).
As a detector used for the X-ray detecting unit of an X-ray diagnostic apparatus, an X-ray film or an I.I. (Image Intensifier) has been used. In an X-ray imaging method using this I.I., X-ray projection data (to be referred to as projection data hereinafter) obtained when X-rays generated by the X-ray generating unit are transmitted through a subject is converted into an optical image by the I.I., and this optical image is displayed on a monitor after being converted into an electrical signal by an X-ray TV camera and digitized. Therefore, the X-ray imaging method using the I.I. allows real-time imaging which is impossible in the film system, and can acquire projection data in the form of digital signals. This makes it possible to perform various kinds of image processing. As a substitute for the above I.I., a flat panel detector comprising a two-dimensional array of detection elements has recently attracted attention. Some of such detectors have already been put into practical use.
FIG. 8 shows a C-arm holding apparatus used for a conventional circulatory organ X-ray diagnostic apparatus. An X-ray generating unit 101 is mounted on one end (lower end) of a C-arm 103 of a C-arm holding apparatus 105, and an X-ray detecting unit 102 comprising, for example, a flat panel detector is mounted on the other end (upper end) of the C-arm 103 so as to face the X-ray generating unit 101. A one-dot dashed line 108 in FIG. 8 represents an imaging central axis (isocenter) which connects the focal point of an X-ray tube in the X-ray generating unit 101 to the center of the flat panel detector of the X-ray detecting unit 102.
The C-arm 103 is held on a stand 105, fixed on a floor surface 106, through an arm holder 104. The C-arm 103 is mounted on an end portion of the arm holder 104 so as to be slidable in the direction indicated by an arrow a. The arm holder 104 is mounted on the upper portion of the stand 105 so as to be pivotal or rotatable in the direction indicated by an arrow b. The stand 105 comprises a stand fixed portion 105a fixed on the floor surface 106 and a stand movable portion 105b which can pivot about the column axis in the direction indicated by an arrow c.
The X-ray generating unit 101 and X-ray detecting unit 102 (to be collectively referred to as an imaging system hereinafter) are set at an optimal position in an optimal direction with respect to a subject (not shown) placed on a table top 107 by sliding the C-arm 103 in the direction a and pivoting the arm holder 104 in the direction b. In addition, the imaging system and the C-arm 103 can be retracted from the subject by pivoting the stand movable portion 105b in the direction c. Retracting the imaging system and the C-arm 103 makes it possible to ensure a working space around the head of the subject for a doctor or an examiner (to be referred to as an operator hereinafter) and facilitate replacement or repositioning of the subject on the table top 107 before or after examination, placement of anesthesia equipment, and the like.
Note that as the arm holder 104 described above, an L-shaped offset arm is generally used as shown in FIG. 8. Making the arm holder 104 have an L shape allows the C-arm 103 to be placed on a side of the table top 107. This makes it possible to move an end portion of the table top 107 in the longitudinal direction to near the stand 105 in the direction indicated by an arrow d. That is, using the L-shaped arm holder 104 makes it possible to enlarge the moving range of the table top 107 and expand the imaging range with respect to the subject. In addition, the L shape of the arm holder 104 have an advantage of being able to ensure a working space around the head of a subject for an operator.
However, the ensurance of a working space or the enlargement of the imaging range by pivoting the stand movable portion 105b or using the L-shaped arm holder 104 has its own limit because the stand 105 is fixed on the floor surface 106, and hence is not necessarily sufficient for the operator.
In order to solve such problems, a method has been proposed in which a ceiling-mounted C-arm holding apparatus having an arm whose one end is pivotally mounted on the ceiling and an arm holder mounted on the other end of the arm is used, and an imaging region of a subject can be arbitrarily set by aligning the position of the pivot axis of the arm with the central line of a table top in the longitudinal direction (see Jpn. Pat. Appln. KOKAI Publication No. 2000-70248).
According to the method disclosed in the above reference, since the arm holder is held on the ceiling through the arm, this holding apparatus has no stand fixed on the floor surface, unlike the conventional floor type C-arm holding apparatus shown in FIG. 8. Therefore, there is no obstacle to the movement of the table top, and the imaging system can be set at an optimal position with respect to any imaging target region of a subject.
However, the C-arm holding apparatus of a circulatory organ X-ray diagnostic apparatus is basically a floor type apparatus. It is therefore necessary for this floor type C-arm holding apparatus to ensure a sufficient work space and allow easy X-ray imaging at an arbitrary position without any limitation on the imaging range. In a dual plane system having an imaging system for cardiac angio, which is used for X-ray imaging with a relatively narrow field of view, and an imaging system for general angio, which is used for X-ray imaging with a wide field of view, e.g., imaging of the head or the lower limbs, two C-arm holding apparatuses, i.e., a floor type apparatus and a ceiling-traveling type apparatus, must be selectively used. When, in particular, the ceiling-traveling C-arm holding apparatus is to be used, it is desired that the floor type C-arm holding apparatus be retracted to an optimal area.